This is EXACTLY what I thought was happening - only I'm not a phone techie, so wasn't sure!

Another strange thing - updated BBM today, with 7.9mb of memory left - BBM was described as being 2.9mb in size. After installation, only 4.9mb left - does this mean the old BBM wasn't removed??

Can any of you guys direct me to a link to easy to follow instructions, to reinstall the O/S or (as aiharkness suggests) a security wipe?

Many thanks, Guys!!

I would try a simple reload first. It will allow you to back-up and reload all of your apps easily. Instructions for doing that can be found here. The loader will ask you if you want to do a back-up and then gives you an opportunity to select what you want to restore. Tip: do not reload language support that you don't use. Keeping this to a minimum seems to free up a lot of memory.

If you need to wipe your device, it is easiest to do that using a tool like BB Swiss Army Knife. BBSAK also includes utilities to back-up and restore your apps.